PM / wakeup: Only update last time for active wakeup sources

When wakelock support was added, the wakeup_source_add() function
was updated to set the last_time value of the wakeup source. This
has the unintended side effect of producing confusing output from
pm_print_active_wakeup_sources() when a wakeup source is added
prior to a sleep that is blocked by a different wakeup source.

The function pm_print_active_wakeup_sources() will search for the
most recently active wakeup source when no active source is found.
If a wakeup source is added after a different wakeup source blocks
the system from going to sleep it may have a later last_time value
than the blocking source and be output as the last active wakeup
source even if it has never actually been active.

It looks to me like the change to wakeup_source_add() was made to
prevent the wakelock garbage collection from accidentally dropping
a wakelock during the narrow window between adding the wakelock to
the wakelock list in wakelock_lookup_add() and the activation of
the wakeup source in pm_wake_lock().

This commit changes the behavior so that only the last_time of the
wakeup source used by a wakelock is initialized prior to adding it
to the wakeup source list. This preserves the meaning of the
last_time value as the last time the wakeup source was active and
allows a wakeup source that has never been active to have a
last_time value of 0.

Fixes: b86ff9820fd5 (PM / Sleep: Add user space interface for manipulating wakeup sources, v3)
Signed-off-by: Doug Berger <opendmb@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 5872705432f8abda47243cf70b8af4d7c7281ebd..36bad46c7c6812594bfa4eee456fdd96bd86267e 100644 (file)
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -183,7 +183,6 @@ void wakeup_source_add(struct wakeup_source *ws)
        spin_lock_init(&ws->lock);
        timer_setup(&ws->timer, pm_wakeup_timer_fn, 0);
        ws->active = false;
-       ws->last_time = ktime_get();
 
        spin_lock_irqsave(&events_lock, flags);
        list_add_rcu(&ws->entry, &wakeup_sources);

diff --git a/kernel/power/wakelock.c b/kernel/power/wakelock.c
index dfba59be190b6a7d36495b7dcfc225a9fba2b0f6..4210152e56f0f403c69f1539cc011ae807e5eee0 100644 (file)
--- a/kernel/power/wakelock.c
+++ b/kernel/power/wakelock.c
@@ -188,6 +188,7 @@ static struct wakelock *wakelock_lookup_add(const char *name, size_t len,
                return ERR_PTR(-ENOMEM);
        }
        wl->ws.name = wl->name;
+       wl->ws.last_time = ktime_get();
        wakeup_source_add(&wl->ws);
        rb_link_node(&wl->node, parent, node);
        rb_insert_color(&wl->node, &wakelocks_tree);